The objective of this proposal is to elucidate the post-transcriptional mechanisms controlling translation and subcellular localization of mRNAs involved in inflammatory responses in bronchial epithelial cells. Epithelial cells of the bronchial airways are directly exposed to the environment and are the first line of defense against airborne particulate matter, allergens and infectious agents. Mounting evidence suggests that bronchial epithelial cells play a pivotal, multifaceted role not only in the maintenance of physico-chemical homoeostasis of the airways but also in the pathogenesis of airway diseases. During allergic airway inflammation, the epithelium is both a source of mediator production as well as a target of remodeling processes. Yet, little is known about post-transcriptional regulation of mediator, effector and remodeling gene expression in these cells during the inflammatory response, and about how this regulation may be altered when airway inflammation becomes persistent, such as in asthma. We have carried out extensive preliminary studies using primary normal or asthmatic human bronchial epithelial (HBE) cells cultured at the liquid-air interface, human bronchial epithelial BEAS-2B cells, and an in vivo mouse model of allergic airway inflammation. The results suggest that bronchial epithelial cells from asthmatics undergo a coordinated alteration of miRNA profile/function and of P- bodies, cytoplasmic domains for storage and/or degradation of translationally repressed mRNAs. These changes lead to a hyperactive state of the protein synthesis that contributes to sustaining excess production of inflammatory mediators and thus perpetuating the chronic nature of asthmatic inflammation. In the proposed study we will: 1) Determine whether a reduction in miR-26 and miR-16 abundance contributes to the persistent, elevated level of IL-6 observed in asthmatic primary HBE cells; 2) Define the role of a group of miRNAs that are significantly down-regulated in asthmatic primary HBE cells in controlling the activity of translation machinery in bronchial epithelial cells; and 3) Determine whether a reduction in P-bodies is a hallmark of activated bronchial epithelial cells, and how alteration of P-body assembly and disassembly influences the inflammatory response in bronchial epithelial cells. The airway epithelium is fundamentally abnormal in asthma, but the molecular and biochemical bases for this abnormality remains largely undefined. We will employ state-of-the-art approaches to gain critical insights into translational regulation of inflammatory mediator production and the pathological mechanism by which this regulation may be altered in bronchial epithelial cells in asthma. The proposed studies involve an unexplored but exciting new area of research in airway inflammation and are likely to introduce novel concepts and methodologies to the field of airway inflammation. The results have a potential for identifying new targets to speed development of new therapeutic approaches to the chronic airway inflammation associated with asthma.